TypeError: console.log(…) is not a function

2017-09-03 20:12:31

Simply put a semicolon (;) after console.log().


Explanation

The error is easily reproducible like this:

It’s trying to pass function(){} as an argument to the return value of console.log() which itself is not a function but actually undefined (check typeof console.log();). This is because JavaScript interprets this as console.log()(function(){})console.log however is a function.

If you didn’t have the console object you’d see

ReferenceError: console is not defined

If you had the console object but not the log method you’d see

TypeError: console.log is not a function

What you have, however, is

TypeError: console.log(...) is not a function

Note the (...) after the function name. With those it’s referring to the return value of the function.


Respect the ;

All these code snippets result in all sorts of unexpected errors if no semicolons are present:

console.log() // As covered before() // TypeError: console.log(...) is not a functionconsole.log() // Accessing property 0 of property 1 of the return value…[1][0] // TypeError: console.log(...) is undefinedconsole.log() // Like undefined-3-3 // NaN

Another Example

You see the (...) oftentimes with the use of chained methods or chained property accessors:

string.match(/someRegEx/)[0]

If that RegEx isn’t found, the method will return null and the property accessor on null will cause a TypeError: string.match(...) is null — the return value is null. In the case of console.log(...) the return value was undefined.


  • 2018-11-01 22:08:19

    Android Toolbar左、中、右对齐

    默认的Android Toolbar中添加子元素view是从左到右依次添加。需要注意的是,Android Toolbar为自身的NavigationIcon(app:navigationIcon)最靠右,Logo(app:logo)紧接NavigationIcon、Title(app:title)接续Logo、保留了默认的位置(从左边到右)。这些Android Toolbar保留的系统设置字段将挤压开发者自己安放在Toolbar中的子view,如图所示:

  • 2018-11-06 06:42:59

    XUtils3框架数据库的基本使用方法

    今天给大家带来数据库模块的讲解,现在主流的ORM框架很多,比如OrmLite,GreenDao,Active Android,Realm等等,这些框架每个都有自己的优点和缺点,大家完全可以根据自己项目的实际需求进行选择,下面开始进入今天的数据库模块的介绍。